This invention is related to a method of fabricating gate valve bodies. Prior art methods of fabricating gate valve bodies involve the welding of unmachined inlet and outlet conduits to a fabricated body structure, then machining the seat ring surfaces, flanges and other surfaces. In order to do the machining at this time very large equipment must be used to precisely and accurately machine the seat ring pockets and other surfaces on the gate valve body structure. This machining process is extremely costly because it is time consuming and it requires very expensive and delicate machinery to accurately produce the required surfaces. In the fabrication and welding of gate valve bodies, they are generally constructed with conduits being welded to sides of the structure from the exterior of the valve body itself. No prior art fabricated gate valve structure is known wherein major welding of the seat assembly is done on the interior of the structure once the conduits are placed in the structure.
Prior art fabricated gate valves are usually stress relieved after they have been welded and before machining in order to minimize the warping and bending due to the welding process and to relieve residual stresses. These gate valves usually do not have a seat structure which will compensate for warpage and misalignment in the seat pocket zones which occur after the seat pockets are machined or while they are being machined.